1. Field of the Invention
The present invention relates to water-soluble polymeric materials for use with wash additives, and more particularly to water-soluble polymeric films for rinse-release of wash additives.
2. Description of the Prior Art
Water-soluble polymeric films are known in the art and described in several references. Such polymeric films are used in packaging materials to simplify dispersing, pouring or dissolving the materials. As used herein "polymer" means a macromolecule made up of a plurality of chemical subunits (monomers). The monomers may be identical or chemically similar, or may be of several different types. Unless a more specific term is used, "polymer" will be taken to include hetero- and homo- polymers, and random, alternating, block and graft copolymers. Water-soluble, film packages of such polymeric materials can be directly added to the mixing vessel, advantageously avoiding contact with toxic or messy materials, and allowing accurate formulation in the mixing vessel. Soluble pre-measured polymeric film pouches aid convenience of consumer use in a variety of applications, particularly those involving wash additives. The use of polyvinyl alcohol (PVA) films to contain laundry products is hampered by the range of wash temperatures typically employed. PVA films of the art general exhibit their greatest solubility in hot water (above 90.degree. F.) with varying degrees of solubility in warm (75.degree. F.) and cold (40.degree. F.) water. As used hereinafter, wash additive refers to those materials which are intended for use, or are most efficacious in a rinse portion of a wash cycle and are intended to improve the aesthetics, feel, appearance, sanitation or cleanliness of fabrics or wares washed in machine washing apparatus. Such wash additives are preferably rinse-added after an alkaline detergent wash has occurred, and include but are not limited to fabric softeners, brighteners, anti-redeposition agents and bleaches. It is desirable to effectuate the release of the additives during the rinse portion, rather than during the wash portion, of the wash cycle. It is further desirable to add these products initially, at the start of the wash cycle, thereby avoiding the need to monitor the cleaning process and add the additives at the beginning of the rinse portion of the wash cycle. Polymeric films used to contain such additives would have to be insoluble during the wash phase, remain insoluble throughout cold, warm, or hot water washes, and become soluble during the rinse phase.
U.S. Pat. No. 4,626,372, issued to Kaufmann et al discloses a PVA film soluble in wash liquors containing borate. Richardson et al. U.S. Pat. No. 4,115,292 shows enzymes embedded in water-soluble PVA strips, which are in turn encased in a water-soluble polymeric film pouch which may be PVA. The PVA may include cellulose as a modifier. Albert, U.S. Pat. No. 3,892,905 discloses a cold-water soluble film which may be useful in packaging detergents. British patent application No. 2,090,603 (Sonenstein) describes a packaging film having both hot and cold water solubility and formed from a blend of polyvinyl alcohol and polyacrylic acid. Haq, U.S. Pat. No. 4,416,791 describes a detergent delivery pouch of a water-soluble PVA layer and a water-insoluble polytetrafluoroethylene layer which encloses a liquid additive. U.S. Pat. No. 4,234,442 issued to Cornelissens discloses a dual package pouch delivering an acidic detergent component and an alkaline detergent component. The pouch is composed of a mixture of different water-soluble polymers. Wong, U.S. Pat. No. 4,108,600 shows a detergent composition in a water-insoluble pouch which is encapsulated with material having a pH dependent solubility to achieve a pH dependent release. Dunlap, U.S. Pat. No. 3,198,170, shows a cold-water soluble detergent packet of PVA containing a granular detergent having a hydrated salt to maintain moisture in the film. Schultz et al U.S. Pat. No. 4,557,852 describes a copolymeric water-soluble film for packaging wash additives. The film comprises a water-insoluble "soft" monomer plus a water-soluble anionic monomer. Pracht et al, U.S. Pat. No. 4,082,678 describes an article for rinse-release of actives consisting of an outer pouch or container which has at least one water-soluble wall, of for example PVA, and an inner receptacle having at least one soluble wall of, for example, PVA or methylcellulose. The inner soluble wall is insolubilized during the wash by an electrolyte or pH control agent which may be sodium borate. Guerry et al, U.S. Pat. No. 4,176,079 describes a wash additive enclosed in a water-soluble polymer of e.g., PVA or methylcellulose. Zimmermann et al, U.S. Pat. No. 4,098,969 shows PVA with boric acid as a means of reducing the solubility of the PVA. Shinetsu, JP No. 54-137047 shows a film of a polyvinyl alcohol phosphate and a nonionic water-soluble cellulose such as methylcellulose.
Accordingly, there remains a need for a water-soluble delivery system for a wash additive, which will remain insoluble during hot, warm, or cold water wash conditions but will rapidly and fully solubilize during rinse conditions to release the wash additives.
It is therefore an object of the present invention to provide a pH dependent, temperature independent, water-soluble additive release means.
It is another object of the present invention to provide a means for delivery of wash additives, which means may be added during a wash portion of a wash cycle and which will deliver the wash additives during a rinse portion thereof.